The present invention concerns the methods and devices implemented to manufacture semiconductors or microelectromechanical systems (MEMS) in semiconductor manufacturing plants. In particular, the invention pertains to means for increasing the yield of semiconductor manufacturing plants.
In a semiconductor manufacturing plant, substrates such as semiconductor wafers and/or masks undergo treatments in process chambers, carrying out various steps such as steps of depositing material and steps of etching. Between each step, the substrates are moved between various equipments.
When microelectronics chips are manufactured, the considerable number of processing steps (about 400 of them) leads to sequencing restrictions between the processing equipment. The substrates are transferred between the equipments. Since wait times between equipment may be long, typically several hours, it is necessary to store the substrates.
Thus, in a semiconductor manufacturing plant, there is provided a plurality of substrate processing equipment, substrate storage means, substrate transport means, and a manufacturing execution system (MES) functionally related with the substrate processing equipment, with substrate storage means and substrate transport means.
The manufacturing execution system (MES) is thereby adapted to control the substrate processing equipment, in order to carry out satisfactory steps of processing. The manufacturing execution system also gives the order to take the substrates out of the storage means, and controls the substrate transport means to lead the substrates to the next processing equipment in the order of the process steps.
Given the number of steps of the process to be implemented, in order to increase manufacturing productivity, substrates have traditionally been processed in batches. It is therefore batches of substrates which are stored, moved, and processed.
But the need to increase productivity persists. To achieve this, it has been sought to automate the movement of batches of substrates, and to optimize these movements. Thus, in order to improve manufacturing output, it has been proposed in document U.S. Pat. No. 7,610,111 to optimize the movement of batches of substrates by examining the orders of priority dictated by the load of the substrate processing equipment, by examining the batches of substrates waiting in the storage means, and by choosing the movements of batches of substrates so as to minimize storage time.